This invention relates to an Sbxe2x80x94Re ammoxidation reaction catalyst, and to a method for manufacturing a corresponding unsaturated nitrile such as methacrylonitrile or the like from a lower hydrocarbon such as isobutylene, isobutane or the like in the presence of both ammonia and a molecular oxygen-containing gas using this Sbxe2x80x94Re ammoxidation catalyst.
An ammoxidation reaction in which ammonia and oxygen were allowed to act on an organic compound and the methyl groups were directly changed into cyano groups is a well-known conventional method for manufacturing an unsaturated nitrile such as acrylonitrile, methacrylonitrile or the like and numerous ammoxidation reaction catalysts have been proposed up to now. For example, proposed catalysts containing molybdenum include an Moxe2x80x94Vxe2x80x94Te-based oxide catalyst (Japanese Laid-Open Patent Application Nos. 02-257, 05-148212, 05-208136, 06-279351, 06-287146, and 07-108101), an Moxe2x80x94Crxe2x80x94Bi-based oxide catalyst (Japanese Laid-Open Patent Application Nos. 06-116225 and 07-215925), an Moxe2x80x94Te-based oxide catalyst (Japanese Laid-Open Patent Application No. 07-215926), an Moxe2x80x94Vxe2x80x94Texe2x80x94Nb-based oxide catalyst (Japanese Laid-Open Patent Application Nos. 08-57319 and 08-141401), an Moxe2x80x94Vxe2x80x94Sbxe2x80x94Nb-based oxide catalyst (Japanese Laid-Open Patent Application No. 09-157241), and an Moxe2x80x94Sbxe2x80x94W-based oxide catalyst (Japanese Laid-Open Patent Application No. 07-157462). Many catalysts containing tungsten have also been proposed, such as a Vxe2x80x94Sbxe2x80x94W-based oxide catalyst (Japanese Laid-Open Patent Application No. 02-261544), a Vxe2x80x94Sbxe2x80x94Wxe2x80x94P-based catalyst (Japanese Laid-Open Patent Application No. 02-95439), a Vxe2x80x94Wxe2x80x94Te-based oxide catalyst (Japanese Laid-Open Patent Application No. 06-228073), a Crxe2x80x94Sbxe2x80x94W-based oxide catalyst (Japanese Laid-Open Patent Application No. 07-157461) and the like.
Ammoxidation reaction catalysts containing antimony have also been proposed, which include, in addition to those listed above, Sbxe2x80x94Sn-based, Vxe2x80x94Snxe2x80x94Sbxe2x80x94Cuxe2x80x94Bi-based, Vxe2x80x94Snxe2x80x94Sbxe2x80x94Cuxe2x80x94Te-based, and other such oxide catalysts (Japanese Laid-Open Patent Application No. 04-275266), a Vxe2x80x94Sbxe2x80x94Ga-based oxide catalyst (Japanese Laid-Open Patent Application No. 06-135922), a Gaxe2x80x94Sb-based oxide catalyst (Soviet Patent Nos. SU547444 and SU698646), Vxe2x80x94Sbxe2x80x94Fe-based, Vxe2x80x94Sbxe2x80x94Ga-based, and other such oxide catalysts (Japanese Laid-Open Patent Application No. 06-135922), a Vxe2x80x94Sbxe2x80x94Te-based oxide catalyst (Japanese Laid-Open Patent Application No. 04-275266), and a Vxe2x80x94Sbxe2x80x94O-based oxide catalyst (Japanese Laid-Open Patent Application No. 11-33399). Further, an oxide catalyst containing molybdenum, tellurium, vanadium, and niobium has also been proposed as an ammoxidation reaction catalyst for manufacturing unsaturated nitrites without lowering the yield or degrading the catalyst (Japanese Laid-Open Patent Application No. 11-124361).
Catalysts containing rhenium (Re) exhibit a distinctive activity in regard to the hydrodesulfurization of crude oil and the dehydrogenation and selective hydration of organic compounds, and for these reactions the activity of a rhenium compound is superior to that of a corresponding catalyst containing molybdenum or tungsten, so rhenium compounds are widely used in many industrial processes, such as the refining of crude petroleum products, the metathesis of alkenes and the like. However, for applications related to catalyst oxidation reactions, all that has been reported is that a rhenium compound will react with ethanol and methanol, and will react as a promoter (catalysts for cobalt, molybdenum, vanadium and the like, for instance) in the selective oxidation of alkenes and aromatics.
Meanwhile, rhenium has been found to be an important element in many active ammoxidation reaction catalysts containing antimony (Sb), as mentioned above. It was not known, though, that Sbxe2x80x94Re compound oxides are useful as ammoxidation reaction catalysts for an aliphatic hydrocarbon.
It is an object of the present invention to provide an ammoxidation catalyst for an aliphatic hydrocarbon such as isobutylene, isobutane or the like, and more particularly an ammoxidation catalyst composed of an Sbxe2x80x94Re compound oxide with which ammoxidation into methacrylonitrile or other such unsaturated nitrile can be performed in the presence of a molecular oxygen-containing gas and ammonia, and to provide a method for manufacturing methacrylonitrile or another such unsaturated nitrile from an aliphatic hydrocarbon such as isobutylene, isobutane or the like using this ammoxidation reaction catalyst composed of an Sbxe2x80x94Re compound oxide.
The inventors conducted diligent research aimed at achieving the stated object, learned that because of the electron configuration of rhenium, an oxide of rhenium has the same electrical potential for the purposes of an ammoxidation catalyst as vanadium (V), molybdenum (Mo), and tungsten (W), and arrived at the present invention upon discovering that when a compound oxide of a rhenium oxide and one of the above-mentioned antimony oxides, and particularly two novel compounds, is produced, and this Sbxe2x80x94Re compound oxide is used as an ammoxidation reaction catalyst in the reaction of isobutylene or isobutane in the presence of ammonia and a molecular oxygen-containing gas, methacrylonitrile is produced very efficiently in the presence of a high concentration of oxygen and ammonia.
Specifically, the present invention relates to a catalyst for the ammoxidation reaction of an aliphatic hydrocarbon, composed of an Sbxe2x80x94Re compound oxide (Claim 1), a catalyst for the ammoxidation reaction of an aliphatic hydrocarbon according to Claim 1, wherein the Sbxe2x80x94Re compound oxide is SbRe2O6 or Sb4Re2O13 (Claim 2), and a catalyst for the ammoxidation reaction of an aliphatic hydrocarbon according to Claims 1 or 2, wherein the aliphatic hydrocarbon is isobutylene or isobutane (Claim 3).
The present invention also relates to a method for manufacturing an unsaturated nitrile, wherein an aliphatic hydrocarbon is subjected to vapor phase contact ammoxidation with ammonia and a molecular oxygen-containing gas in the presence of an Sbxe2x80x94Re compound oxide catalyst (Claim 4), a method for manufacturing an unsaturated nitrile according to Claim 4, wherein the Sbxe2x80x94Re compound oxide is SbRe2O6 or Sb4Re2O13 (Claim 5), a method for manufacturing an unsaturated nitrile according to Claims 4 or 5, wherein the aliphatic hydrocarbon is isobutylene or isobutane, and the unsaturated nitrile is methacrylonitrile (Claim 6), a method for manufacturing an unsaturated nitrile according to any of Claims 4 to 6, wherein the vapor phase contact ammoxidation is carried out under conditions in which the concentration ratio of the aliphatic hydrocarbon, ammonia, and oxygen is 1:(1.5-5):(2-5) (Claim 7), and a method for manufacturing an unsaturated nitrile according to any of Claims 4 to 7, wherein the vapor phase contact ammoxidation is carried out at a high temperature of 400 to 600xc2x0 C. (Claim 8).